Optical and Photocatalytic Properties of Cobalt-Doped LuFeO₃ Powders Prepared by Oxalic Acid Assistance

B-site cobalt (Co)-doped rare-earth orthoferrites ReFeO₃ have shown considerable enhancement in physical properties compared to their parent counterparts, and Co-doped LuFeO₃ has rarely been reported. In this work, LuFe_1-xCo_xO₃ (x = 0, 0.05, 0.1, 0.15) powders have been successfully prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method at 1100 °C for 2 h. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies demonstrated that a shrinkage in lattice parameters emerges when B-site Fe ions are substituted by Co ions. The morphology and elemental distribution were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The UV-visible absorbance spectra show that LuFe_0.85Co_0.15O₃ powders have a narrower bandgap (1.75 eV) and higher absorbance than those of LuFeO₃ (2.06 eV), obviously improving the light utilization efficiency. Additionally, LuFe_0.85Co_0.15O₃ powders represent a higher photocatalytic capacity than LuFeO₃ powders and can almost completely degrade MO in 5.5 h with the assistance of oxalic acid under visible irradiation. We believe that the present study will promote the application of orthorhombic LuFeO₃ in photocatalysis.